Forty years after Democratic rising star Robert F. Kennedy was killed at a Los Angeles hotel during his presidential run, new evidence suggests the man serving a life sentence for his murder did not fire the shots that killed the charismatic senator.

Forensic scientists met at a conference in Connecticut this week to discuss their independent findings that cast serious doubt on the Kennedy assassination. Sirhan Sirhan is serving a life sentence in Kennedy's death, but the conference presenters argue he could not have fired the fatal shot that killed Kennedy.

One investigator, Dr. Robert Joling, has studied the Kennedy assassination for nearly four decades. He determined the fatal shot came from behind Kennedy, while Sirhan was four to six feet in front of the senator and never got close enough to shoot him from behind, an NBC affiliate reports.

Analysis by another forensics engineer, Philip Van Praag, of a Canadian journalists tape recording, known as the Pruszynski recording, determined that 13 shots were fired while Kennedy was killed, although Sirhan's gun only held eight bullets, according to the NBC reporter. This suggests that a second shooter was involved in the assassination.

Van Praag's analysis led him to conclude that a second gun that was fired matched a type owned by one of the security guards in Kennedy's entourage.

"When that security guard was asked about owning that gun at first he admitted, 'Yes I owned that kind of gun but I got rid of it two months before the assassination.'" correspondent Amy Parmenter said on MSNBC Wednesday. "It turns out upon further investigation, in fact, he did not get rid of that gun until five months after the shooting. Of course, you can see where we're going with this. ... That security guard, was in fact behind Senator Kennedy when the fatal shot was fired."